Centrifugal switches are a safety feature that prevents the heating element from operating when the drum is not rotating. Currently, dryers use centrifugal switches to ensure that the heating element does not operate when the drying compartment (i.e. drum) is not rotating. Generally, centrifugal switches used in dryers are normally open and as the drum reaches a minimum rotation speed, the switches are “thrown” to the closed position, thereby completing the circuit and allowed the heating element to receive power. Should the drum stop rotating or the rotation speed fall below the minimum rotation speed, the centrifugal switch returns to the normally open position, thereby breaking the circuit and cutting power to the heating element.
There is a long restart time for gas heating elements. In other words, after power has been cut from the heating elements, there is a long delay in returning the heating element to the same heat output as before the power was cut. For reversible dryers the long restart time presents a significant problem for dryers in which the drum shall change directions multiple times throughout a drying cycle. The restart time can add significant time to the drying cycle. For electric dryers the centrifugal switch typically carries higher current and reversible dryers would cause unnecessary activation and deactivation (i.e. “short cycling”) of the heating element. This would in return reduce the useful life (i.e. reliability) of the centrifugal switch. Simple removing or totally bypassing the centrifugal switch is not an option because removing or totally bypassing the centrifugal switch would remove an important safety feature that prevents runaway heating element conditions. That is, removing the centrifugal switch may lead to the heating element being energized when the drum is stationary for extended periods of time.
Having the above identified problems in mind, there exists a need for a dryer having a configuration that would allow the heating element to remain energized when the drum slows and reverses rotational direction while still preventing the heating elements from remaining energized while the drum is stationary for extended periods of time.